Plug-in electrical heating unit



Sept. 9, 1969 R. KEFAUVER, JR 3,465,426

PLUG-IN ELECTRICAL HEATING UNIT Filed Oct. 6, 1967 2 Sheets-Sheet 1 INVENTOR Les-r52 .QKecAuvelz ATTORNEYS P 1969 R. KEFAUVER, JR 3,466,426

PLUG-IN ELECTRICAL HEATING UNIT Filed Oct. 6. 1967 2 Sheets-Sheet 2 \9 3 1* m 3 m o N m l 3 g m INVENTOR 00 7 Les-r512 (2.;KEFAUVEQ 17 ATTORNEYS United States Patent 3,466,426 PLUG-IN ELECTRICAL HEATING UNIT Lester R. Kefauver, Jr., Lanham, Md., assignor to Electro- Therm Inc., Laurel, Md., a corporation of Maryland Filed Oct. 6, 1967, Ser. No. 673,367 Int. Cl. H05b 3/76 US. Cl. 219451 12 Claims ABSTRACT OF THE DISCLOSURE A surface type plug-in electrical heating unit for electric ranges, wherein the surfaces heating unit has a tubular sheathed heating element in a spirally coiled configuration terminating in a pair of laterally spaced, side-by-side end portions or legs having a pair of parallel, elongated contact pins projecting therefrom defining the male contact members. A grounding bracket is secured to and extends between the sheath legs and has an elongated grounding pin extending therefrom in parallelism with the contact pins. A simple female receptacle member defines contact sockets for the contact pins and the grounding pin, and is formed simply of a unitary housing block having a substantially uniform cross-section throughout of electrically insulating, temperature resistant material provided with three parallel cylindrical bores extending entirely therethrough axially aligned with the male contact pins and grounding pin, each of these bores having seated therein hollow conductive tubular sleeves or bushings preconnected to respective lead wires and restrained in position within the bores by shoulder formations and outwardly and rearwardly inclined protrusions spaced therefrom which embrace therebetween oppositely facing abutment surfaces within the bore to securely hold the sleeves against withdrawal. The internal diameters of the sleeves are sized to slidably receive, and establish good electrical contact with, the contact pins and the grounding pin.

The present invention relates in general to a plug-in electrical heating unit of the type commonly employed as the surface heating unit in electric range tops and the like, having one or more tubular sheated heating elements adapted to support cooking utensils thereon, wherein the heating element is removably supported in an opening in the range top and is releasably coupled with a female receptacle fitting or socket assembly in the range which may be supported by the range or free-floating.

Heretofore, many surface type electric heating units have been provided for electric range tops, wherein the heating unit is removable from the electrically disconnectable with respect to the electric range. Such units have customarily employed either a single tubular sheathed heating element, or a pair of such heating elements, in spirally coiled configuration having a pair, or two pairs, of terminal end portions or legs of the sheath extending in laterally spaced side-by-side relation, located generally below the coiled portion and projecting beyond the perimeter of the coil. The terminal legs have been provided with various types of prong or male contact configurations projecting from the ends of the legs to be releasably coupled with various types of female receptacle fittings provided in the stove assembly. Customarily the receptacle fitting provided for such plug-in type electrical units has been of quite complex construction, usually involving insulation material housings which are a highly irregular and involved interior configuration, frequently formed by mating housing halves, and usually requiring a large number of metallic parts to be assembled in a special manner within the housing to provide for electrical connection of the male contacts with the electrical supply circuit.

An object of the present invention is the provision of "ice a novel plug-in electrical heating element assembly of the surface type for use with electric ranges and the like, which is exceedingly simple in construction and can be manufactured at low cost.

Another object of the present invention is the provision of a novel plug-in electrical heating element assembly for electric range tops and the like, wherein the female receptacle fitting into which elongated contact pins projecting from the ends of the heating elements are to be removably inserted is simply constructed of a suitably formed insulating block of substantially uniform crosssection throughout having a plurality of parallel bores extending therethrough housing tubular contact sleeves secured in the housing bores and electrically connected to supply wiring, the sleeves being sized and located to slidably receive and establish electric contact with the contact pins.

Another object of the present invention is the provision of a novel plug-in electric heating unit as described in the immediately preceding paragraph, wherein the contact sleeves are restrained in selected location within the housing bores by shoulder formations adjacent the wire ends thereof and by outwardly protruding teeth inclining away from the direction of insertion of the sleeves into the bores to facilitate assembly of the receptacle fitting.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a top plan view of a plug-in electric heater assembly constructed in accordance with the present invention;

FIGURE 2 is a section view of the assembled plug-in heating unit and adjacent portions of the electric range, taken along the line 22 of FIGURE 1;

FIGURE 3 is an exploded perspective view of the plug-in receptacle fitting and adjacent terminal end portions of the electric heater unit;

FIGURE 4 is a section view, to enlarged scale, through the plug-in receptacle fitting, taken along the line 44 of FIGURE 3, and

FIGURE 5 is a section view similar to FIGURE 4 showing a modification of the receptacle fitting.

Referring to the drawings, wherein like reference characters designate corresponding parts throughout'the several figures, the surface type electrical heating unit, indicate generally by the reference character 10, in accordance with conventional construction practices, comprises a heating element 11 of conventional tubular sheathed resistor type having a metallic tubular sheath and a helical coil of resistor wire embedded in compacted electrical insulation within the sheath, the heating element 11 being shaped to define a spirally coiled portion lying in a plane and forming the heat generating portions of the heating element, and a pair of opposite end portions or legs, indicated by the reference characters 12, 13, which are bent downwardly from the plane of the spirally coiled portion to a lower level at which the terminal end portions extend outwardly in side-by-side relation beyond the perimeter of the spirally coiled portion. The coiled portion of the heating element 11 constitutes the active portion of the heater and is preferably fiat at the top to provide fiat faces for conductivity of heat to a utensil placed thereon. In accordance with common practice, the helical coil of resistance wire within the sheath of the heating element 11 extends through the length of the coiled portion and has its opposite ends electrically connected at the ends of the spirally coiled portion to low resistance, axially elongated terminal pins which extend along the legs 12, 13 and project outwardly beyond the end of legs 12, 13, the exposed end forming contact pins 14, 15. The outer ends of the legs 12, 13 are sealed against entrance of moisture by providing suitable plugs, for example, of compressible heat resistant material, which encircle the respective terminal pins 14, 15 and are inserted in the sheath ends so as to fit snugly therein under compression around the pins against the interior of the sheath ends to be securely retained in place.

The coiled portion of the heating element 11 is suitably supported on a spider assembly 16, formed for example of three metallic strap members or legs arranged in a generally triangular pattern with their outer end portions welded together. The outermost convolution of the heating element coil portion may be secured to the spider assembly 16, for example, by means of a holding bracket 17 welded to and between the outermost ends of the spider legs at a location opposite the heater legs 12, 13, the bracket 17 having a portion which rises above the upper edge of the spider legs and has a concave recess therein adapted to receive the outermost convolution of the heating element and be crimped about the same to securely hold the heating element. The longer heating element leg 12 may also be stabilized relative to the spider assembly 16 in the region where it curves downwardly from the plane of the coiled portion by means of depending supporting bracket 18, which is secured to the crosswise leg of the spider assembly and extends downwardly to bear against the sheath leg 12. If desired, a suitable medallion 19 may be releasably held in place in the central region of the triangle defined by the spider legs, for example, by inwardly pressed ridges on the spider legs frictionally engaging in confronting indentations or recesses in the side of the medallion.

This surface type electrical heating unit is designed to be removably supported in one of the openings provided in a conventional range top 20, for example, on a removable reflector pan 21, having an outwardly projecting annular top flange 22, designed to rest on an inwardly projecting bottom flange 23 of a conventional adaptor ring or trim ring 24 which rests on the range top adjacent the opening and depends through the range top opening, as is well known in the art.

A transversely extending grounding bracket or bridge plate 25 is provided with a pair of apertures located and sized to receive the opposite sheath legs 12, 13 therethrough, the bounding portions of the apertures being crimped firmly to at least one of the sheath end portions or otherwise suitably secured thereto, and includes an enl-ongated grounding pin 26 supported in a third aperture in the grounding bracket between and below the two terminal contact pins 14, along an axis paralleling the axes of the contact pins and extending somewhat beyond the outer or free ends of the contact pins. In one suitable arrangement, the grounding pin 26 is provided with an enlarged head 26a and a plurality of outwardly projecting protrusions or tooth formations 26b of sufiicient thinness to be somewhat resiliently deformable, inclining towardthe head 26a and spaced at the free edges thereof from the head a distance approximating the thickness of the plate 25. This construction is such that the grounding pin 26 can be inserted through the aperture therefor in the grounding plate until the protrusions 2611 are flexed inwardly by the aperture walls and pass through the aperture, whereupon the protrusions elastically return to their outwardly flaring positions to bear against the face of the grounding plate 25 opposite the head 26a and firmly clamp the grounding pin 26 in the plate 25. Alternatively, the ground pin 26 may be Welded or riveted to the grounding plate, if desired.

The female receptacle fitting forming a plug-in housing into which the terminal contact pins 14, 15 and grounding pin 26 are removably inserted to establish the electrical supply to the heating element is of very simple construction and is indicated by the reference character 30. This receptacle fitting 30, which forms the socket component of the plug-in connection, comprises a housing body 31 of substantially uniform transverse cross-section throughout its length, formed as an integral body of suitable temperature resistant material, preferably a known high temperature phenolic resin, which may be either molded to assume the illustrated configuration, or extruded to this approximate configuration, or a ceramic material which can be molded to the desired configuration. This housing body has three bore 32, 33 and 34, extending throughout its longitudinal extent, each of uniform crosssection over the major axial extent thereof, interrupted by a slightly constricted or smaller diameter collar formation 32', 33, 34 of short axial length intermediate the ends of the bores. The upper bores 32 and 33 are disposed in side-by-side relation with their axes in a common horizontal plane and spaced a distance corresponding to the spacing between the axes of the terminal contact pins 14, 15, while the third bore 34 is located equi-distant between the axes of the bore 32 and 33 and either below or above the common plane thereof, depending upon whether the grounding pin 26 is below or above the contact pin, at an appropriate position to receive the grounding pin 26. These bores open through both the front end wall 35 and the rear end wall 36 of the housing body 31. The upper bores may, if desired, have a slightly enlarged diameter at their extreme ends, facing the contact pins, sized in correspondence with the diameter of the plugs on the sheath ends to receive the plugs therein, or all of the bores may be of the same diameter throughout except for the constructed collar formations. In the illustrated embodiment, the body 31 is of three lobed cross-sections providing two horizontally aligned, opposite convex or semi-cylindrical lobes substantially concentric with the bores 32, 33 and a depending centered lower lobe of like contour concentric with lower bore 34.

Electrically conductive contact surfaces resembling liners are provided at the interior walls of the bores 32, 33 and 34, by simple tubular, longitudinally split contact sleeves or bushings 37, 38 and 39, formed of any currentcarrying metal sheet material bent to substantially tubular configuration having an axial length to extend from the rear or distal ends of the bores to the enlarged cavities at the entrance ends, and having outer diameters approximately equal to the inner diameter of the bores 32, 33 and 34. The wire conductor cores of conventional supply wiring harnesses 40 are securely fixed in the rear end portions of the contact sleeves 37, 38 and 39 in any suitable manner, as by soldering the wire conductor cores within the rear portions of the contact sleeves, and if desired, surrounding portions of the contact sleeves may be deformed inwardly to clamp the supply conductor cores therein to further assist in retention of the wires in the contact sleeves. These contact sleeves 37, 38 and 39 are provided adjacent their rear or wire ends with forwardly facing stop shoulder formations 41, for example by flanges or segments projecting radially outwardly from the sleeves, and intermediate their ends have outwardly extending, inclined tooth formations or protrusions 42 having sharp free edges spaced from the stop formations 41 in correspondence with the axial length of the collars 32, 33 and 34', the protrusions inclining in diverging relation toward the rear ends of the contact sleeves or in a direction opposite the direction of insertion of the sleeves into the bores 32, 33 and 34. It will be apparent, therefore, that upon driving or insertion of the contact sleeves 37, 38 and 39 into the bores 32,33 and 34 from the rear ends of the bores, the protrusions 42 are elastically deformed inwardly by the constricted collar formations towards the axes of the sleeves by the bore walls to pass therethrough and then spring outwardly when the stop shoulders 41 reach the rearwardly facing shoulders of the collar formations, the free edges of the protrusions 42 at this position abutting the forwardly facing shoulders of the collar formations to restrain the sleeves against withdrawal and securely clamp the sleeves in the mating bores therefor.

The housing body 31 lends itself to production in a simple manner or by a number of different procedures, such as by molding a single housing body, or an elongated, substantially uniform cross-section casting of proper length for a plurality of such housing bodies, in an appropriately configurated mold, or by extruding a long extrusion adequate for a large number of such housing bodies, having an appropriate cross-sectional configuration, and then cutting transversely through the extrusion to segregate the extrusion into the individual housing bodies 31. If the body is extruded, the bores extruded therein would be of proper diameter for the collar formations, and the larger diameter portions may then be formed by subsequent boring to enlarge the appropriate regions of the bores.

Thus, an exceedingly simple socket type receptacle fitting is provided which is readily assembled merely by inserting the contact sleeves 37, 38 and 39 into the mating bores 32, 33 and 34 therefore from the rear of the housing body, the stop shoulders 41 and outwardly and rearwardly flaring protrusions 42 acting to securely clamp the contact sleeves within the mating bores 32, 33 and 34 of the housing body at the desired position.

A simple hanger clip 43 is also preferably assembled onto the housing body 31, the hanger clip 43 being formed of sheet metal and shaped to provide a body portion 44 of substantially C-shaped cross section conforming to the upper portion of the housing body 31 defining the two upper, horizontally aligned lobes to embrace the outwardly convex lateral portions, these lobes being concentric with the upper bores 32 and 33. The clip 43 also has an integral rearwardly projecting tongue 45 extending in parallelism with the longitudinal axis of the housing body from the hanger clip body portion 44. The tongue 45 is designed to project rearwardly from the housing body 31, and is sized to fit in the usual slot or screw opening customarily provided in the lip, indicated at 46 in FIGURE 2, at the lower edge of the downwardly projecting cylindrical flange bounding the range top opening 20.

When the female receptacle fitting is pulled outwardly into the range top opening during removal of the heating element for cleaning, the hanger clip tongue 45 can be inserted in this slot in the lip 46 (or the similar screw slot provided in the depending cylindrical flange if no lip 46 is present) to hold the receptacle fitting in accessible position against accidental return underneath the stove top. If a stationary receptacle mount rather than a free floating arrangement is desired a mounting bracket having a portion adapted to be screwed to the flange or flange lip surrounding the range top opening, and having a body portion similar to that of the clip 43 may be used in a manner which will be apparent to persons skilled in this art to support the fitting from the range top.

While the preferred embodiment herein illustrated includes a constricted bore portion to define annular stop shoulders to be embraced between the stop formation 41 and protrusions 42 to restrain the sleeves 37, 38 and 39 with the insulator body, the constricted bore portions 32, 33', 34' and the enlargement at the entrance end for the end plugs may be omitted, leaving the bores of the modified housing body 31' of precisely uniform diameter throughout, as illustrated in FIGURE '5. When this housing body 31' is used, the stop formations 41' may be sized to have a larger diameter perimeter than the bore diameter, as illustrated in broken lines in FIGURE 5.

In such case the protrusions 42 will still bite into or so tightly about the bore walls as to restrain the sleeves against withdrawal from the positions to which they are driven or forced within the bores. The stop formations 41 also may be optionally omitted, if desired, as indicated by the solid lines in FIGURE 5, relying solely upon the tooth-like protrusions 42 to secure the sleeves in position within the bores.

While only one specific embodiment of the invention has been particularly shown and described, it will be apparent that various modifications may be made therein within the spirit and scope of the invention, and it is desired, therefore, that only such limitataions be placed thereon as are imposed by the prior art and set forth in the appended claims.

I claim:

1. A plug-in surface electrical heating unit for electric ranges comprising a spirally coiled sheath type heating element having a pair of laterally spaced cylindrical terminal pins extending parallel to a reference axis from the sheath ends forming a pair of male contact pins, a female receptacle fitting for removably receiving said terminal pins for communicating an electrical supply thereto comprising a solid integral insulator body extending along said reference axis having a substantially uniform transverse cross-section throughout its axial length and having proximal and distal end faces relative to said heating element, said body having a plurality of substantially cylindrical bores opening through said proximal and distal faces and extending entirely therethrough along axes paralleling said reference axis and aligned with the axes of said contact pins for respectively receiving the contact pins, said bores each having a cylindrical tubular hollow sleeve of electrically conductive material therein extending over the major axial length of the associated bore having outer and inner diameters corresponding substantially to the inner bore diameter and the outer contact pin diameter to tightly fit in said bores and slidably receive the contact pins in electrically conductive relation therein, electrical conductors conneted to the sleeves adjacent the distal face of said body, and said sleeves having integral restraining formations thereon admitting insertion of the sleeves into said bores only from said distal face and effecting restraining engagement with the bore walls when disposed within the bores to resist Withdrawal of the sleeves through said distal face.

2. A plug-in surface electrical heating unit as defined in claim 1, wherein said heating element includes a grounding plate member secured to and extending transversely between end portions of the heating element sheath in electrically conductive relation therewith, said grounding plate member having a generally cylindrical grounding contact pin in electrically conductive communication therewith extending therefrom along an axis paralleling and spaced transversely from the terminal pin axis to a position projected beyond the ends of said terminal pins, and said bores of said insulator body including a bore aligned with the axis of said grounding contact pin for removably receiving the same.

3. A plug-in surface electrical heating unit as defined in claim 2, wherein said pair of terminal pins are arranged in side-by-side relation in a horizontal plane and said grounding contact pin is located substantially centrally between and spaced vertically from said pair of terminal pins, and the bores of said insulator body associated with the three contact pins being arranged to define a first pair of bores whose axes lie in a common horizontal plane for receiving said pair of terminal pins and a third bore for said grounding contact pin.

4. A plug-in surface electrical heating unit as defined in claim 1, wherein each of said bores includes a slightly constricted bore portion over a minor portion of its axial length intermediate its ends defining annular stop shoulder surfaces facing respectively toward said proximal and distal ends, said sleeves each including a radially outwardly projecting shoulder formation at a selected axial position along the sleeve to abut the shoulder surface facing toward said distal end and limit the extent of insertion of the sleeve into the bore from said distal end, and said restraining formations including integral toothlike protrusions inclining outwardly from the sleeve and toward said distal face to be elastically deformed inwardly by said constricted bore portion for passage therethrough during insertion of the sleeve into the bore and elastically return the free edges of the protrusions outwardly following such passage into restraining abutment with the shoulder surface facing toward said proximal end.

5. A plug-in surface electrical heating unit for electric ranges comprising a spirally coiled sheath type heating element having a pair of laterally spaced cylindrical terminal pins extending parallel to a reference axis from the sheath ends forming a pair of male contact pins, a female receptacle fitting for removably receiving said terminal pins for communicating an electrical supply thereto comprising a solid integral insulator body extending along said reference axis having a substantially uniform transverse cross-section throughout its axial extent and proximal and distal end faces relative to said heating element, said body having a plurality of cylindrical bores respectively associated with the contact pins opening through said proximal and distal faces and extending entirely therethrough along axes paralleling said reference axis and aligned with the axes of said contact pins, said bores each having surface means defining stop shoulder formations facing toward the proximal and distal ends of the body, a cylindrical tubular hollow sleeve of electrically conductive material in each of said bores extending over the major axial length of each bore having outer and inner diameters corresponding substantially to the inner bore diameter and the outer contact pin diameter to slidably receive the latter in electrically conductive relation therein, electrical conductors connected to the sleeve adjacent the distal face of said body, and said sleeves having integral restraining formations thereon admitting insertion of the sleeves into said bores from said distal face and effecting restraining engagement with said stop shoulder formations when disposed within the bores to hold the sleeves against axial displacement.

-6. A plug-in surface electrical heating unit as defined in claim 5, wherein said restraining formation on each of said sleeves comprises integral tooth-like protrusions deformed in said sleeves intermediate the opposite ends thereof inclining outwardly beyond the cylindrical exterior surfaces of the sleeves and toward said distal face to be elastically deformed inwardly by the bore walls during insertion of the sleeves into the bores from said distal face and maintain restraining contact with said stop shoulder formations in said bores resisting withdrawal of the sleeves from said bores.

7. A plug-in surface electrical heating unit as defined in claim 5, wherein the surface means in each of said bores comprises a slightly constricted bore portion over a minor portion of its axial length intermediate its ends defining annular stop shoulder surfaces facing respectively toward said proximal and distal ends, said sleeves each including a radially outwardly projecting shoulder formation at a selected axial position along the sleeve to about the shoulder surface facing toward said distal end and limit the extent of insertion of the sleeve into the fore from said distal end, and said restraining formations including integral tooth-like protrusions inclining outwardly from the sleeve and toward said distal face to beelasti cally deformed inwardly by said constricted bore portion for passage therethrough during insertion of the sleeve into the bore and elastically return the free edges of the protrusions outwardly following such passage into restraining abutment with the shoulder surface facing toward said proximal end.

8. A plug-in surface electrical heating unit as defined in claim 1, wherein said insulator body is a molded body of high temperature resistant phenolic material cast to define the shape of the insulator body recited.

9. A plug-in surface electrical heating unit as defined in claim 1, wherein said insulator body is an extruded body of high temperature resistant phenolic material having uniform transverse cross-section throughout substantially the entire length of the body including said bores.

10. A plug-in electrical heating unit as defined in claim 3, wherein said insulator body is of three-lobed external configuration of uniform transverse cross-section throughout its axial extent defining a pair of oppositely directed convex upper lateral lobes of substantially semi-cylindrical configuration concentric with the axes of said upper pair of bores and a lower downwardly convex lobe of substantially semi-cylindrical configuration concentric with the axis of said lower bore.

11. A plug-in electrical heating unit as defined in claim 2, wherein said grounding contact pin comprises an elongated integral pin member having a generally cylindrical shank terminating at one end in a tapered tip and at the other end in an enlarged head, said plate member having an aperture of substantially the diameter of said shank to accommodate passage of the shank therethrough, and said shank having integral deformed protrusions in lateral surface portions thereof inclining outwardly and toward said head which are sufliciently elastically deformable to be distorted radially inwardly by contact with the bounding surface of said aperture during insertion of the shank therethrough to permit passage of the protrusions through said aperture, said protrusions elastically returning radially outwardly following passage through said aperture to dispose the free edges thereof in clamping contact with a face of said plate member when said head engages an opposite face of the plate member.

12. A plug-in electrical heating unit as defined in claim 1, wherein the bores in said insulator body each has a single diameter extending from said distal face to a location closely adjacent said proximal face providing an uninterrupted cylindrical wall extending between said distal face and said location whose diameter corresponds closely to the diameter of the sleeves consisting of elastically deformable integral tooth-like members extending outwardly from the perimeter thereof along inclined paths diverging toward said distal face to be forced inwardly upon abutment with said cylindrical walls sufficiently to permit insertion of the sleeves into the bores from said distal face and having such continuous contact with said cylindrical walls at their free ends as to resist widthdrawal of the sleeves toward said distal face when the sleeves are fully inserted into the bores.

References Cited UNITED STATES PATENTS 2,672,532 3/ 1954 Robinson 200-5188 1,265,513 5/1918 Preston 200-51.88 3,016,444 1/ 1962 Sasidnowski 21945 1 3,021,414 2/1962 Sand 21945 1 3,200,237 8/ 1965 Hanson 21945 1 BERNARD A. GILHEANY, Primary Examiner F. E. BELL, Assistant Examiner 

